Reflective Surface Treatments for Optical Sensors

ABSTRACT

An electronic device includes one or more light emitters for emitting light toward an object and one or more light detectors for collecting light exiting the object. A reflective coating, surface, or surface finish can be applied adjacent to the area to which light is emitted and/or through which light exits in order to increase the light collected by the light detector. The reflective coating can be oriented so as to reflect light back into the object.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a nonprovisional patent application of, and claimsthe benefit to, U.S. Provisional Patent Application No. 62/043,294,filed Aug. 28, 2014 and titled “Reflective Surface Treatments forOptical Sensors,” the disclosure of which is hereby incorporated hereinby reference in its entirety.

FIELD

This disclosure relates generally to sensor devices, and moreparticularly to electronic devices incorporating one or more opticalsensing systems.

BACKGROUND

An electronic device can include an optical sensing system forquantifying surface or subsurface characteristics of an object ontowhich the electronic device is placed. The optical sensing system caninclude a light emitter to illuminate the object with light that may beabsorbed or reflected by the object in a manner related to thecharacteristics of the surface or subsurface thereof. The opticalsensing system may also include a light detector to generate electricalsignals corresponding to light reflected from the object as a result ofthe illumination. These signals can be conveyed to the electronic deviceby the optical sensing system so that the electronic device can quantifycharacteristics of the surface or subsurface of the object.

In many cases, the electronic device may be undesirably responsive tonoise (e.g., resulting from ambient light) present in the signalsconveyed to it by an optical sensing system.

SUMMARY

Certain embodiments described herein reference an electronic deviceconfigured to quantify subsurface characteristics of an object ontowhich the electronic device is placed. In one aspect, an electronicdevice can be adapted to obtain physiological data from a biologicalsubject after being placed in contact with or proximate to a surface ofthe subject. For example, an electronic device such as a wearablefitness device can be positioned against the skin of a user's wrist(hereinafter the “measurement site”) and can obtain therefrom certainphysiological data about the user such as heart rate, respiration rate,blood oxygenation, blood pressure, and so on.

In many embodiments, an electronic device (such as a smart watch,fitness device, cellular phone, tablet computer, other computing device,exercise equipment, exercise monitor, physiology monitor, and so on) caninclude an optical sensing system positioned behind or within one ormore apertures defined within a bottom surface of the electronic device.The optical sensing system can include a light emitter (e.g., a lightemitting diode) for illuminating a measurement site of an object and alight detector (e.g., a photodiode, a phototransistor, and/or an opticalimage sensor) for receiving light reflecting from the measurement site.In one aspect, the light emitter can be oriented to emit light toward aportion of the measurement site most adjacent to the light emitter(hereinafter the “illumination area”). Similarly, the light detector canbe oriented to receive light exiting a portion of the measurement sitemost adjacent to the light detector (hereinafter the “collection area”).In many cases, the illumination area may be adjacent to the collectionarea. For example, in one embodiment, the illumination area and thecollection area can be spaced one centimeter apart.

The electronic device can also include one or more reflectors positionedon or nearby the surface and adjacent to the one or more aperturesdefined therein. In some examples, the reflectors can be formed frommirrored films and can be positioned around the perimeter of theapertures.

Additional embodiments described herein may reference lenses positionedwithin each of the apertures defined by the bottom surface, disposedrespectively over the light emitter and the light detector. One or moreof the lenses may be formed from the same material as the surface,although this is not required. In one embodiment, one or more of thelenses can be configured to diffuse light. In other embodiments, one ormore of the lenses can be configured to focus light onto a particularpoint or along a particular direction. In other embodiments, one or moreof the lenses can be configured to polarize light to a particularorientation. In other embodiments, one or more of the lenses may beconfigured to exhibit transparency to a first frequency band of lightand to exhibit opacity to a second frequency band of light. In oneexample, the first frequency band of light can be infrared light and thesecond frequency band of light can be green light. In some embodiments,a reflector as described above can be positioned around the perimeter ofa bottom surface of a lens. In other embodiments, a lens can be formedfrom a multi-layered laminate material and a reflector can beinterstitially disposed between the layers thereof. In some examples,each lens can be configured to provide the same functionality, althoughthis is not required of all embodiments. For example, in some cases,different lenses can be configured to provide different functionality.For example, a lens positioned over a light emitter can be configured tofocus light from the light emitter into the measurement site whereas alens positioned over a light detector can be configured to focus lightexiting the measurement site onto the light detector.

Still further embodiments described herein reference a method of opticalsensing, including at least the operations of emitting light toward ameasurement site of an object, receiving light exiting a first sub-areaof the measurement site, and reflecting light exiting a second sub-areaof the measurement site back into the measurement site.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference will now be made to representative embodiments illustrated inthe accompanying figures. It should be understood that the followingdescriptions are not intended to limit the disclosure to one preferredembodiment. To the contrary, each is intended to cover alternatives,modifications, and equivalents as may be included within the spirit andscope of the described embodiments and as defined by the appendedclaims.

FIG. 1A depicts a top plan view of an example electronic device.

FIG. 1B depicts a bottom plan view of the example electronic device ofFIG. 1A, showing separated apertures associated with an optical sensingsystem defined within a bottom surface of the example electronic device.

FIG. 2A depicts a simplified cross-section view of a light emitter and alight detector of an optical sensing system taken through section A-A ofFIG. 1B.

FIG. 2B depicts the simplified cross-section view of FIG. 2A, showing aset of example light reflection and absorption paths from the lightemitter, through a measurement site of a subject, to the light detectorof the optical sensing system.

FIG. 3A depicts a bottom plan view of a wearable electronic deviceshowing an optical sensing system implemented with one example of areflector.

FIG. 3B depicts an example cross-section of FIG. 3A taken throughsection B-B, showing a simplified view of the optical sensing system ofFIG. 3A.

FIG. 3C depicts an alternative example simplified cross-section of FIG.3A taken through section B-B, showing a simplified view of the opticalsensing system of FIG. 3A implemented with a bottom surface having aconvex curvature.

FIG. 3D depicts the simplified cross-section of FIG. 3A, showing a setof example light reflection and absorption paths from a light emitter,through a measurement site of a subject, to a light detector of theoptical sensing system of FIG. 3A.

FIG. 3E depicts an alternative example simplified cross-section of FIG.3A, showing a set of example light absorption and reflection paths froma light emitter, through a measurement site of a subject, to a lightdetector of the optical sensing system of FIG. 3A implemented with abottom surface having a convex curvature.

FIG. 4A depicts a bottom surface of an example electronic device with areflector adapted for use with an optical sensing system.

FIG. 4B depicts a bottom surface of an example electronic device withanother reflector adapted for use with an optical sensing system.

FIG. 5 depicts a bottom surface of an example electronic device withanother reflector adapted for use with an optical sensing system.

FIG. 6A depicts a bottom surface of an example electronic device withanother reflector adapted for use with an optical sensing system.

FIG. 6B depicts a bottom surface of an example electronic device withanother reflector adapted for use with an optical sensing system.

FIG. 7 depicts example operations of a method of operating an opticalsensing system in accordance with embodiments described herein.

The use of the same or similar reference numerals in different drawingsindicates similar, related, or identical items.

The use of cross-hatching or shading in the accompanying figures isgenerally provided to clarify the boundaries between adjacent elementsand also to facilitate legibility of the figures. Accordingly, neitherthe presence nor the absence of cross-hatching or shading conveys orindicates any preference or requirement for particular materials,material properties, element proportions, element dimensions,commonalties of similarly illustrated elements, or any othercharacteristic, attribute, or property for any element illustrated inthe accompanying figures.

DETAILED DESCRIPTION

Reference will now be made in detail to representative embodimentsillustrated in the accompanying drawings. It should be understood thatthe following descriptions are not intended to limit the embodiments toone preferred embodiment. To the contrary, it is intended to coveralternatives, modifications, and equivalents as can be included withinthe spirit and scope of the described embodiments as defined by theappended claims.

Embodiments described herein reference systems and methods forincreasing the speed, sensitivity, accuracy, precision, and/orreliability of optical sensing systems configured for use with smallform factor electronic devices, such as wearable devices, although thevarious systems and methods described herein are not limited toparticular form factors and can apply equally to larger embodiments.Further, it should be appreciated that the various embodiments describedherein, as well as the functionality, operation, components, andcapabilities thereof may be combined with other elements as necessary,and so any physical, functional, or operational discussion of anyelement, feature, structure, or interrelation is not intended to belimited solely to a particular embodiment to the exclusion of others.Moreover, although many embodiments described herein reference opticalsensing systems configured to provide functionality such as fitness orhealth tracking or physiological data collection to a wearableelectronic device, one may appreciate that the various systems andmethods described herein are not limited to use of optical sensingsystems in this manner. In other words, the various optical sensingsystems as described herein (and methods associated therewith) can beused to detect, sense, or quantify other biological or non-biologicalproperties of a user, another biological subject, a non-biologicalobject or surface, or for any other purpose. For example, an opticalsensing system can be used to detect subsurface characteristics of amaterial during a manufacturing process to determine whether thematerial should be rejected or accepted. In another example, an opticalsensing system can be disposed onto or into a veterinary or medicaldiagnostic tool (e.g., wand, pen, etc.) that can be placed against apatient's skin in order to obtain physiological characteristics of saidpatient. Such a medical diagnostic tool can be used, in one example,with multiple patients in an emergency setting to assist veterinary ormedical professionals with triage decisions.

Many embodiments described herein reference an optical sensing systemdisposed below a convex surface defining two apertures symmetricallyspaced about the principal axis of the curve. A light emitter of theoptical sensing system can be positioned behind one aperture and a lightdetector of the optical sensing system can be positioned behind theother aperture. In this manner, when the optical sensing system isplaced in contact with a measurement site, the light emitter and thelight detector can be optically isolated from one another by the apex ofthe convex curvature.

More particularly, because the apex of the convex curvature is theportion of the surface extending outwardly the farthest, the apex willcontact the surface of a prospective measurement site first, therebyforming an opaque boundary with the measurement site that opticallypartitions the illumination area from the collection area. In theseembodiments, the quantity of light exiting the collection area afterbeing affected by the characteristics of the subsurface of themeasurement site (hereinafter the “subsurface-affected light”) may begreater than the quantity of light reflecting directly from the surfaceof the measurement site (hereinafter the “surface-reflected light”)because surface-reflected light may be substantially or entirely blockedby the optical barrier established by the convex curvature of thesurface.

Further embodiments can incorporate an optically reflective materialdisposed on, within, or adjacent to the apertures defined by the convexsurface. In these embodiments, the optically reflective material can bedisposed about the perimeter of the apertures respectively associatedwith the light emitter and the light detector of the optical sensingsystem. More particularly, the optically reflective material may bedisposed and oriented to reflect light onto or into the measurementsite. In this manner, both surface-reflected light andsubsurface-affected light that exits the measurement site outside of thecollection area can be reflected back into the measurement site(hereinafter the “recovered light”), thereby increasing the quantity ofsubsurface-affected light received by the light detector.

In one non-limiting alternative phrasing, these embodiments canincorporate reflective materials so as to direct as much light aspossible into the subsurface of the measurement site so that said light,via specular or diffuse reflection, may have one or more additionalchances to be reflected toward the collection area. Thus, in theseembodiments, the quantity of subsurface-affected light received by thelight detector of the optical sensing system may be greater than thequantity of subsurface-affected light received by the light detector ofembodiments omitting said reflective material.

Optical sensing system embodiments described herein can exceed theperformance of conventional optical sensing systems unable todiscriminate between surface-reflected light and subsurface-affectedlight while orienting the light emitter and light detector to face thesame surface. Particularly, in many conventional examples, the quantityof surface-reflected light received by a light detector may predominatethe quantity of subsurface-affected light received by the same. As aresult, many conventional optical sensing systems require a substantialamount of data over a substantial period of time in order to account forthe effects of noise and to detect and quantify characteristics of themeasurement site.

Conversely, an electronic device incorporating optical sensing systemsas described herein may quantify surface and/or subsurfacecharacteristics of a measurement site onto which the electronic deviceis placed with increased speed, accuracy, and precision.

Example electronic devices that can incorporate optical sensing systemsas described herein can include, but are not limited to, a telephone, aheadset, a pulse oximeter, a digital media player, a tablet computingdevice, a laptop computer, a desktop computer, a timekeeping device, aperipheral input device (e.g., keyboard, mouse, trackpad), a sportsaccessory device, a wearable device, a medical diagnostic device, abiometric authentication device, and so on.

For example, in one embodiment, an electronic device incorporating anoptical sensing system in accordance with embodiments described hereincan be worn by a user so as to obtain physiological data from the usersuch as, but not limited to, heart rate data, blood pressure data,temperature data, oxygen level data, and so on. The wearable electronicdevice incorporating such an optical sensing system can provide to theuser, or a third party authorized by the user, diet or nutritioninformation, medical reminders, physiological tips or information, orother raw or processed physiological data.

In these embodiments, the optical sensing system may be included withina housing that encloses the internal components of the wearableelectronic device. In another example, an optical sensing system may bepartially or entirely separate from the wearable electronic device. Inthese examples, the wearable electronic device can include one or morecommunication channels, either wired or wireless, to facilitatecommunication with the external optical sensing system.

In addition to the optical sensing system, the wearable electronicdevice can include other sensors or sensor systems configured to obtainphysiological data from a user. Example sensors can include, but may notbe limited to, movement sensors, orientation sensors, temperaturesensors, electrodermal sensors, blood pressure sensors, heart ratesensors, respiration rate sensors, oxygen saturation sensors,plethysmographic sensors, activity sensors, pedometers, blood glucosesensors, body weight sensors, body fat sensors, blood alcohol sensors,dietary sensors, and so on.

As with other embodiments described herein, an optical sensing systemincorporated by a wearable electronic device can be implemented with alight emitter and a light detector. As noted above, the optical sensingsystem can be configured to measure changes in the light reflected froma measurement site, such as a wrist of a user.

As used herein, the phrases “reflected from a measurement site” and“exiting a measurement site” (in addition to similar phrases orterminology) generally refer to both surface-reflected light and tosubsurface-affected light that originated from a light emitter and, viaspecular or diffuse reflection from the surface or subsurface of themeasurement site, have become oriented to propagate away from themeasurement site.

More particularly, the optical sensing system of a wearable electronicdevice can orient a light emitter to illuminate a portion of the user'swrist. As noted above, this portion of a measurement site is generallyreferred to herein as “the illumination area.” The optical sensingsystem can also orient the light detector to receive light exiting aseparate portion of the user's wrist. As noted above, this portion ofthe measurement site is generally referred to herein as “the collectionarea.”

In some cases, light from the light emitter may be reflected (specularlyand/or diffusely) by the surface of the user's wrist. As noted above,this light is generally referred to herein as “the surface-reflectedlight.” In other cases, light from the light emitter can penetrate thesurface of the user's wrist and can be absorbed or reflected (specularlyor diffusely) by the subsurface of the wrist. As noted above, this lightis generally referred to herein as “the subsurface-affected light.” Inmany cases, the amount of absorption or reflection provided by aparticular measurement site at a particular time may depend upon thecharacteristics of the measurement site at that time. In other words,surface-reflected light may vary predictably with the characteristics ofthe surface of the measurement site and, similarly, subsurface-affectedlight may vary predictably with the characteristics of the subsurface ofthe measurement site.

For example, the tissue of the user's wrist can absorb or reflect lightdifferently depending on physiological characteristics of the surface(e.g., skin, hair, sweat) or subsurface (e.g., stratum corneum of theskin, dermis, blood vessels beneath the skin, and so on) of the user'swrist. For example, sweat on the user's wrist can affect the quantity orquality of surface-reflected light.

In another example, a user's heartbeat can affect the quantity orquality of subsurface-affected light received by the light detector.More particularly, the user's heartbeat can affect an increase ordecrease in the user's blood volume within the user's wrist. Thisperiodic distention and contraction is commonly referred to as theuser's pulse. As a direct result of changes in the volume of bloodproximate to the measurement site, the light absorption capacity of themeasurement site may correspondingly increase or decrease which, inturn, can cause the amount of subsurface-affected light received by thelight detector to increase and decrease with the user's pulse. This typeof volumetric data collection via optical sensing is conventionallyreferred to as photoplethysmographic data collection (hereinafter“PPG”).

As noted above, the light detector of an optical sensing system canreceive light exiting the collection area and generate electricalsignals corresponding thereto. In certain embodiments, light exiting thecollection area can include a component corresponding tosurface-reflected light and a component corresponding tosubsurface-affected light. In certain embodiments implementing anoptical barrier between the light emitter and light detector (e.g., theapex of a concave surface associated with the optical sensing system),the component corresponding to the surface-reflected light can besubstantially reduced or eliminated. In these embodiments, theelectrical signals generated by the light detector may correspondsubstantially only to subsurface-affected light.

In many embodiments, the electrical signals generated by the lightdetector of the optical sensing system can be conveyed as data to thewearable electronic device which, in turn, can utilize the data toquantify one or more physiological characteristics of the user at thattime. In many examples, data from the light detector can includeinformation about the collected light such as the chromaticity,brightness, frequency, and/or luminance of the light.

Optical sensing systems as described herein can also be used to obtainnon-physiological information or data. For example, the wearableelectronic device can use the optical sensing system as a surface audiosensor (e.g., microphone). In other examples, a wearable electronicdevice can use the optical sensing system as an input device (e.g.,wrist-tap input). In still further embodiments, the wearable electronicdevice can use an optical sensing system to determine a state of theelectronic device (e.g., connected to a user, connected to a charger,sitting on a surface such as a table, and so on). In another example, anoptical sensing system can be used as a liveness verification forbiometric authentication or security embodiments.

Accordingly, optical sensing systems incorporated by embodimentsdescribed herein may serve as multi-purpose sensors.

These and other embodiments are discussed below with reference to FIGS.1A-7. However, those skilled in the art will readily appreciate that thedetailed description given herein with respect to these Figures is forexplanatory purposes only and should not be construed as limiting.

FIG. 1A depicts a top plan view of an example wearable electronic device100. In the illustrated embodiment, the wearable electronic device 100may be implemented as a portable electronic device that is adapted to beworn by a user such as a smart watch. Other embodiments can implementthe wearable electronic device 100 differently. For example, thewearable electronic device 100 can be a smart phone, a gaming device, adigital music player, a sports accessory device, a medical device, adevice that provides time and/or weather information, a fitness device,and other types of electronic devices suitable for attaching to a user.

The wearable electronic device can be implemented as a fitness devicethat provides physiological information (whether real-time or not) tothe user, authorized third parties, and/or an associated monitoringdevice. The wearable fitness device may be configured to providephysiological information or data such as, but not limited to, heartrate data, blood pressure data, temperature data, blood oxygensaturation level data, diet/nutrition information, medical reminders,physiological tips or information, or other physiological data. Theassociated monitoring device may be, for example, a tablet computingdevice, a phone device, a personal digital assistant, computer, and soon.

The wearable electronic device 100 can be configured in the form of awearable communications device. A wearable communications device mayinclude a processor coupled with or in communication with a memory, oneor more sensors, one or more communication interfaces, output devicessuch as displays and speakers, one or more input devices, and a fitnessor health tracking system. The communication interfaces can provideelectronic communications between the communications device and anyexternal communication network, device or platform, such as but notlimited to wireless interfaces, Bluetooth interfaces, universal serialbus interfaces, Wi-Fi interfaces, TCP/IP interfaces, networkcommunications interfaces, or any conventional communication interfaces.The wearable communications device may provide information regardingtime, health, statuses of externally connected or communicating devicesand/or software executing on such devices, messages, video, operatingcommands, and so forth (and may receive any of the foregoing from anexternal device), in addition to communications. For simplicity ofillustration, the wearable electronic device 100 is depicted in FIG. 1Awithout many of these elements, each of which may be included,partially, optionally, or entirely, within a housing 102.

The housing 102 can be configured to, at least partially, surround adisplay 104. In many examples, the display 104 may incorporate an inputdevice configured to receive touch input, force input, and the likeand/or may be configured to output information to a user, such asvarious health parameters or physiological suggestions. The display 104can be implemented with any suitable technology, including, but notlimited to, a multi-touch or multi-force sensing touchscreen that usesliquid crystal display (LCD) technology, light emitting diode (LED)technology, organic light-emitting display (OLED) technology, organicelectroluminescence (OEL) technology, or another type of displaytechnology. A button (not shown) might take the form of a home button,which may be a mechanical button, a soft button (e.g., a button thatdoes not physically move but still accepts inputs), an icon or image onthe display 104 or on an input region, and so on. Other buttons ormechanisms can be used as input/output devices, such as a speaker, arotary input device, a microphone, an on/off button, a mute button, or asleep button.

Additionally, the housing 102 can form an outer surface or partial outersurface and protective case for the internal components of the wearableelectronic device 100. In the illustrated embodiment, the housing 102 isformed into a substantially rectangular shape, although thisconfiguration is not required.

The housing 102 can be formed of one or more components operablyconnected together, such as a front piece and a back piece or a topclamshell and a bottom clamshell. Alternatively, the housing 102 can beformed of a single piece (e.g., uniform body or unibody). The housing102 can be coupled to a coupling mechanism used to attach to a user. Forexample, as illustrated, the housing 102 can be coupled to a bandsuitable for attaching to a user's wrist. The band can include a firstband portion 106 and a second band portion 108. The first band portion106 can be configured to join with or couple to the second band portion108 around the user's wrist, thereby removably attaching the wearableelectronic device 100 to the user. The wearable electronic device 100may include one or more sensors configured to obtain physiologicalinformation or data from a user. In some cases, these sensors can beconfigured to operate via non-invasive optical sensing. In such anembodiment, one or more optical sensors configured for obtaininghealth-related and/or physiological information from a user can bedisposed adjacent to a bottom surface of the housing 102.

FIG. 1B depicts a bottom plan view of the wearable electronic device ofFIG. 1A, showing two sensor windows 114 a, 114 b associated with anoptical sensing system. In many cases, an optical sensing system can bea distributed system such that one portion of the optical sensing systemis positioned proximate to one of the two sensor windows 114 a, 114 bwhereas another portion of the optical sensing system is positionedproximate to another of the two sensor windows 114 a, 114 b. In stillfurther embodiments, an optical sensing system can be disposed proximateto a single sensor window. In still further embodiments, an opticalsensing system can be disposed proximate to more than two sensorwindows. In still further examples, an optical sensing system can bedisposed in another manner that incorporates the optical sensing systemwithin an optical circuit that includes a measurement site or ameasurement subject.

An optical sensing system can include a light emitter and a lightdetector (not shown in FIG. 1B, see, e.g., FIG. 2A). In manyembodiments, the light emitter can be configured to illuminate a portionof a measurement site and a light detector can be configured to receivelight exiting the measurement site. In these examples, the light emittercan be a light emitting diode and the light detector can be aphotodiode, phototransistor, and/or an optical image sensor. In otherembodiments, a light emitter and a light detector can be formed from thesame material and/or may be formed as the same component, such as aphototransistor. In these examples, the light emitter and light detectorcan each operate as the other element. Accordingly, for certainembodiments described herein, a light emitter may be operable tofunction as a light emitter in a first mode (e.g., light emitting mode)and also operable to function as a light detector in a second mode(e.g., light receiving mode). Similarly, a light detector may beoperable to function as a light detector in a first mode (e.g., lightreceiving mode) and also operable to function as a light emitter in asecond mode (e.g., light emitting mode). The light emitter and the lightdetector of the optical sensing system are not shown in FIG. 1B forsimplicity of illustration, although it may be understood that the lightemitter and the light detector can be disposed entirely or partiallywithin the housing of the wearable electronic device 100.

By monitoring the output from the light detector of the optical sensingsystem, the wearable electronic device 100 can quantify physiologicalinformation related to the measurement site or related to the user ofthe wearable electronic device 100.

For one non-limiting example, the light emitter of the optical sensingsystem of the wearable electronic device 100 can be configured to emitgreen light toward the skin of the user's wrist. Some of the light maybe reflected by the skin and some of the light may penetrate the skin. Aportion of the penetrating light may be absorbed while another portionof the penetrating light can be reflected, exit the wrist, and returntoward the wearable electronic device 100 (e.g., subsurface-affectedlight). The green light exiting the skin of the wrist can be received bythe light detector and correlated to physiological properties of thesubsurface of the user or the user's wrist. For example, a small amountof green light received by the light detector may correspond to a highamount of absorption which, in turn, may indicate a high volume of bloodwithin blood vessels below the skin, which in turn may correspond to anejection portion (e.g., higher blood pressure) of the user's cardiaccycle.

In many embodiments, the light emitted by the light emitter may bespecifically regulated (hereinafter the “modulated light”). For example,light emitted by the light emitter can have a selected frequency,amplitude, color, direction, and/or modulation pattern. In theseembodiments, the light received by the light detector can be demodulatedprior to further signal processing (hereinafter the “demodulatedlight”), thereby attenuating or eliminating the components of the signalfrom the light detector associated with interference (e.g., noise).

In many embodiments, the light emitter can be disposed adjacent to asensor window 114 a and the light detector can be disposed adjacent to asecond window 114 b. In some embodiments, the light emitter may bepositioned within the housing behind the first sensor window 114 a andthe light detector may be positioned within the housing behind thesensor window 114 b. In many cases, the sensor windows 114 a, 114 b canbe formed from optically-transparent lenses or covers that are disposedabove the light emitter and light detector within apertures definedwithin the bottom surface 112.

As used herein, the term “optically transparent” and variants thereofdoes not necessarily mean that the referent structure is transparent toall visible or invisible light. Instead, the phrase is generally used toindicate transparency or translucency to the particular wavelength oflight emitted by the light emitter and/or received by the light detectorfor a particular embodiment. Thus, some optically transparent sensorwindows may be substantially transparent to infrared light whileblocking visible light. In other examples, some optically transparentsensor windows may be substantially transparent to a particularwavelength of visible light while blocking other frequency bands ofvisible light. In other embodiments, some optically transparent sensorwindows may have electrically or thermally variable transparency oropacity. For example, some embodiments can include sensor windows with aliquid crystal diode layer positioned between one or more polarizers. Inthese examples, the optically transparent sensor window can be opticallytransparent in a first mode and optically opaque (or substantiallyopaque) in a second mode.

In some embodiments, the sensor windows 114 a, 114 b can cooperate withthe bottom surface 112 of the housing 102 to form a convex shape. Inthese examples, the sensor windows 114 a, 114 b may be separated fromone another, disposed symmetrically (or asymmetrically) about theprincipal axis of the convex curvature of the bottom surface 112.

In these embodiments, the bottom surface 112 can curve outwardly fromthe housing 102, defined by a particular radius of curvature. In someexamples, the sensor windows 114 a, 114 b can be disposed such that thecentral axis of each respective sensor window is perpendicular to aplane tangent to the curvature of the bottom surface 112. In otherwords, each sensor window can be oriented at an angle from the principalaxis of the curvature of the bottom surface 112 such that the externalsurface of each sensor window forms a substantially continuous surfacewith the portions of the bottom surface 112 adjacent thereto (see, e.g.,FIG. 3C).

In some examples, the light emitter and light detector can be orientedto be parallel to the axis through the center of each respective sensorwindow. In other words, the light emitter may be configured to emitlight parallel to the axis through the center of the sensor window 114 aand the light detector may be configured to receive light directedparallel to the axis through the center of the sensor window 114 b. Inother examples, the light emitter and light detector can be oriented tobe parallel to one another. In these embodiments, the light emitter canbe oriented to emit light in a direction parallel to the principal axisof the convex curvature and the light detector may be configured toreceive light directed parallel to the principal axis of the convexcurvature.

In some embodiments, the sensor windows 114 a, 114 b can take a shapethat is discontinuous with the shape of the bottom surface 112. Forexample, the sensor windows 114 a, 144 b protrude from or depress intothe bottom surface 112 in a manner that breaks the continuity of theshape of the bottom surface 112. In other examples, the sensor windows114 a, 114 b can be substantially flat. In till other examples, thesensor windows 114 a, 114 b, can take a concave and/or convex shape soas to protrude from or depress into the bottom surface 112. In otherembodiments, the sensor windows 114 a, 114 b can take a different shape.

In these embodiments, the curvature of the housing itself can provide anoptical barrier between the light emitter and the light detector (see,e.g., FIG. 3C). The optical barrier between the light emitter and thelight detector can improve the performance of the optical sensing systemby reducing the amount of surface-reflected light received by the lightdetector.

More specifically, in many embodiments, the apex of the convex curvatureof the bottom surface 112 can physically and optically separate thelight emitter from the light detector when the wearable electronicdevice 100 is positioned on a measurement site. In other words, theportion of the bottom surface 112 extending outwardly the farthest(which will contact the measurement site first) will ensure opticalseparation between the light emitter and light detector. In this manner,any modulated light received by the light detector will have eitherpassed through the measurement site (e.g., subsurface-affected light) orwill result from an external source (e.g., hereinafter the “externalnoise”). As noted above, external noise can be effectively mitigated oreliminated via demodulation of the light received by the light detector.

Thus, absent an optical barrier between the light emitter and the lightdetector, the light detector can receive both modulatedsurface-reflected light and modulated subsurface-affected light. Asnoted above, modulated surface-reflected light can predominate modulatedsubsurface-affected light which, in turn, can cause physiologicalcharacteristics of the subsurface to be substantially obscured,distorted, or otherwise concealed.

Accordingly, many embodiments described herein implement a selectedradius of curvature of the bottom surface 112 so as to reduce the amountof surface-reflected light received by the light detector and toincrease the amount of subsurface-affected light received by the lightdetector. For example, the greater the radius of curvature of the bottomsurface 112, the greater the angle between the axis of the sensor window114 a and the axis of the sensor window 114 b may become. In someembodiments, the convex curvature of the bottom surface 112 can take asubstantially spherical convex shape. In other embodiments, the convexcurvature of the bottom surface 112 can take a parabolic convex shape.

In many embodiments, and as illustrated, the sensor windows 114 a, 114 bcan be separated by a selected distance either symmetrically orasymmetrically about the apex of the convex curvature of the bottomsurface 112. In other examples, the sensor windows 114 a, 114 b can bedisposed in other locations.

For example, in embodiments implemented with closely-spaced (e.g.,adjacent to the apex of the convex curvature) sensor windows, thequantity of light lost to absorption within the measurement site candecrease thereby increasing the quantity of subsurface-affected lightreceived. On the other hand, for closely-spaced sensor windows, thequantity of surface-reflected light may also increase as a result of therelative proximity of the light emitter and the light detector.

Conversely, in examples implemented with sensor windows spaced a greaterdistance apart (e.g., closer toward the perimeter of the bottom surface112), the quantity of light lost to absorption within the measurementsite may increase, potentially decreasing the quantity ofsubsurface-affected light received. However, the quantity ofsurface-reflected light may also decrease.

In a non-limiting alternate phrasing of the considerations presentedabove, the measurement site may appear more brightly illuminated to thelight detector if the sensor windows 114 a, 114 b are sufficiently closeto one another, but may appear too dimly illuminated if the sensorwindows 114 a, 114 b are positioned too far apart. Similarly, the lightdetector may collect a greater proportion of light corresponding only tosubsurface events if the sensor windows 114 a, 114 b are sufficientlyfar apart, but the light emitter may emit too much light for the lightdetector to detect subsurface events if the sensor windows 114 a, 114 bare too close together.

Accordingly, the distance separating the sensor windows 114 a, 114 b mayvary from embodiment to embodiment and may depend upon the outputcapacity of the light emitter, the sensitivity of the light detector,the modulation pattern or scheme associated with the optical sensingsystem, and/or the characteristics of the measurement site.Alternatively or additionally, the output of the light emitter, thesensitivity of the light detector, and/or the modulation pattern orscheme used by the optical sensing system can each be selected based, inpart, upon the distance separating the sensor windows 114 a, 114 b, thelocations of which may be fixed or influenced by the layout ofcomponents, certain manufacturing tolerances, certain materialselections, certain assembly considerations, certain aestheticpreferences, and so on.

In many embodiments, the distance separating the sensor windows 114 a,114 b (and, correspondingly the distance separating the light emitterand light detector) can be defined by the placement of apertures withinthe housing of the wearable electronic device 100. For example, asillustrated, the sensor windows 114 a, 114 b can be disposed withincircular apertures defined within the bottom surface 112, each centeredapproximately half a radius length from the center of the bottom surface112.

Furthermore, although many embodiments are described herein withreference to optical sensors disposed within axially-symmetricconvexly-curved surfaces, such a configuration may not be required ofall embodiments. For example, in other embodiments, the bottom surface112 of the wearable electronic device 100 can be formed to take theshape of a pitched roof. In another embodiment, the bottom surface 112can be formed to take the shape of an arch. In other embodiments, thebottom surface 112 can include a protrusion that physically separatesthe sensor windows. In still further examples, the bottom surface 112can be flat, faceted, or concave. In further embodiments, the bottomsurface 112 can take an arbitrary shape. In other embodiments, thesensor windows 114 a, 114 b can be disposed within a convexly curvedbottom surface without being oriented to follow the curve thereof. Inother words, the sensor windows 114 a, 114 b can be disposed so as to beparallel to the principal axis of the curvature of the bottom surface112.

FIG. 2A depicts a simplified cross-section of FIG. 1B taken throughsection A-A, showing a simplified view of the optical sensing system ofFIG. 1B. The optical sensing system includes a light emitter 116 and alight detector 122 both coupled to a controller 200. In many examples,the controller 200 can be implemented as a processor, a digital circuit,an analog circuit, or any combination thereof, that is configured toperform and/or coordinate one or more operations of the optical sensingsystem or the wearable electronic device 100. In one embodiment, thecontroller 200 can be coupled to a processor associated with thewearable electronic device 100. In another embodiment, the controller200 can be a processor associated with the wearable electronic device100 such that the controller 200 is configured to perform and/orcoordinate the interoperation of the various components of the wearableelectronic device 100 such as, but not limited to, driving a display,receiving input from a touch or force sensor, receiving input from abutton or rotary dial, communicating with other electronic devices via acommunication channel, distributing power from a battery, and so on.

In one embodiment the light emitter 116 may be a light emitting diodeconfigured to emit light at a particular frequency. For example, incertain embodiments the light emitter 116 can be configured to emitgreen light. In another example, the light emitter 116 can emit infraredlight. In still further examples, the light emitter 116 can beconfigured to emit light in another frequency band.

The light detector 122 can be a photodiode, phototransistor, and/or anoptical image sensor such as a charge-coupled device (“CCD”) orcomplementary metal-oxide semiconductor (“CMOS”) array.

The light emitter 116 can be disposed within the housing of the wearableelectronic device and can be positioned below the sensor window 114 a.In one example, the light emitter 116 can be disposed within a cavity118 defined within the housing of the wearable electronic device. Inthese examples, the cavity 118 can be defined by the housing such thatthe cavity 118 is axially aligned with the central axis of the sensorwindow 114 a. In many cases, the interior of the cavity 118 can bepainted with a reflective surface treatment. In some embodiments, thecavity 118 may have a shorter width than that of the sensor window 114 aso as to form a shelf therewith, although this configuration is notrequired. In some examples, the cavity 118 can be filled with a fillermaterial. In some examples, the filler material can be opticallytransparent. In other examples, the filler material can be opticallydiffusive.

A lens 120 or window may seal the cavity 118; the lens 120 need notfocus or scatter light in any particular fashion. The lens 120 may beformed from the same material as the bottom surface 112, although thisis not required. In one embodiment, the lens 120 can be configured todiffuse light, while in other embodiments it may focus light or may notaffect the directionality of light passing therethrough. In someembodiments, the lens 120 may be optically transparent. In still furtherembodiments, the lens 120 may be configured to exhibit transparency in afirst frequency band of light and to be opaque in a second frequencyband of light. For one example, the first frequency band of light can beinfrared light and the second frequency band of light can be visiblelight.

As with the light emitter 116, the light detector 122 can be disposedwithin the housing of the wearable electronic device and can bepositioned below the sensor window 114 b. In one example, the lightdetector 122 can be disposed within a cavity 124 defined within thehousing of the wearable electronic device. As with the cavity 118, thecavity 124 can be defined by the housing such that the cavity 124 isaxially aligned with the central axis of the sensor window 114 b. Inmany cases, the interior of the cavity 124 can be painted with areflective surface treatment. In many examples, the cavity 124 can besealed with a lens 126.

As with the lens 120, the lens 126 can be configured to diffuse light.In other embodiments, the lens 126 may be optically transparent, or maybe shaped to focus light to a particular focal point. In still furtherembodiments, the lens 126 may be configured to exhibit transparency in afirst frequency band of light and to be opaque in a second frequencyband of light. For one example, the first frequency band of light can beinfrared light and the second frequency band of light can be visiblelight.

FIG. 2B depicts a second cross-section like that of FIG. 2A, now showinga set of example light paths from a light emitter through a measurementsite 110 of a subject to a light detector of the optical sensing system.As illustrated, light emitted from the light emitter 116 passes into anillumination area 130 of the measurement site 110, through anintermediate volume 128 of the measurement site 110, to a collectionarea 132 of the measurement site 110, and, thereafter, exits thecollection area 132 where it may be collected by the light detector 122and conveyed to the wearable electronic device 100 via the controller200 (not shown). In many embodiments, the subject may be a human user.As illustrated, point-terminated light vectors represent light absorbedby the measurement site or another material. Similarly, arrow-terminatedlight vectors represent light reflected either specularly or diffusely.

As illustrated, a portion of the light emitted from the light emitter116 may not exit the intermediate volume 128 through the collection area132. For example, some light may continue transmitting in a directionparallel to the length of the intermediate volume 128. In addition, somelight can transmit in directions away from the collection area 132. Inaddition, some light can be absorbed within the intermediate volume,depicted in FIG. 2B as point-terminated lines. Accordingly, the quantityof light received by the light detector 122 may be less than thequantity of light emitted by the light emitter 116.

FIG. 3A depicts a bottom plan view of a wearable electronic device 300showing an optical sensing system having reflective surface treatments.As with the embodiment depicted in FIG. 2A, the wearable electronicdevice 300 can include two separated sensor windows 314 a, 314 bassociated with a light emitter and a light detector of an opticalsensing system, respectively. In addition, the wearable electronicdevice 300 can include a reflector 330 that surrounds the sensor windows314 a, 314 b. The reflector 330 can also include an extended portion 332that extends toward the sensor window 314 b from the sensor window 314a. The extended portion 332 can provide a reflective surface to theentire area between the sensor windows 314 a, 314 b. It should beappreciated that various embodiments may have more or fewer apertures,more or fewer light emitters and more or fewer light detectors.

In many examples, and as illustrated in FIG. 3A, the reflector 330 canbe disposed on an outer surface of the bottom surface 312. In theseexamples, the reflector 330 can be disposed onto the bottom surface 312via an adhesive. In another embodiment, the reflector(s) and/orreflective surface(s) can be disposed onto the bottom surface 312 viaanother means such as vapor deposition, laser etching, pressure bonding,welding, and so on.

In still further embodiments the reflector(s) and/or reflectivesurface(s) can be disposed below the outermost surface of the bottomsurface 312. For example, in some cases, the bottom surface 312 can beformed from a laminate material. In these examples, the reflector(s)and/or reflective surface(s) can be intestinally disposed between layersof the laminate material.

In still other examples, the reflector(s) and/or reflective surface(s)can be disposed onto or into the sensor windows 314 a, 314 b. Forexample, in one embodiment, the reflector 330 can be disposed onto anouter surface about the perimeter of the sensor windows 314 a, 314 b. Inanother example, the reflector 330 can additionally or separately bedisposed onto a sidewall of the sensor windows 314 a, 314 b. In anotherexample, the reflector 330 can be additionally or separately disposedonto a sidewall of a cavity and/or aperture defined within the bottomsurface 312. In still further embodiments, the reflector 330 can bedisposed onto, attached to, or adhered to other portions of the bottomsurface 312, the sensor windows 314 a, 314 b, or any other portion ofthe wearable electronic device 300 suitable for reflecting light backinto a measurement site.

In still further embodiments, the reflector 330 can be oriented toreflect light in a particular direction. For example, the reflector 330disposed most adjacent to the sensor window 314 a can be positioned,oriented, disposed, or configured to reflect light generally toward thesensor window 314 b. Similarly, the reflector 330 disposed most adjacentto the sensor window 314 b can be positioned, oriented, disposed, orconfigured to reflect light generally toward a center point of thesensor window 314 b. In this manner, various areas of the reflector 330can be configured to reflect light in different directions. In manycases, the different directions that different areas of the reflector330 are configured to reflect toward may be selected, at least in part,on the positioning of a light emitter and a light detector of an opticalsensing system with which the reflector 330 is associated. Moreparticularly, many embodiments can configure the reflector 330 toreflect light generally toward a light detector of an optical sensingsystem.

As noted with respect to other embodiments described herein, thereflector 330 and the extended portion 332 can be formed from anysuitable optically reflective material such as glass, crystal, sapphire,zirconia, metals, and so on. In certain embodiments, the reflectivesurface can be configured to be optically transparent in one frequencyband of light and optically reflective in another frequency band oflight. As a non-limiting example, the reflector 330 may be configured toreflect infrared light while absorbing red light. In other examples, thereflector 330 can be configured to reflect more than one frequency bandof light. For example, certain embodiments may include a configurationin which the reflective surface reflects green light and infrared lightwhile substantially absorbing all other frequencies of light.

FIG. 3B depicts a simplified cross-section of FIG. 3A taken throughsection B-B, showing a simplified view of the optical sensing system ofFIG. 3A. As with the embodiment depicted in FIGS. 2A-2B, the opticalsensing system includes a light emitter 316 and a light detector 322. Inone embodiment the light emitter 316 may be a light emitting diodeconfigured to emit light at a particular frequency. For example, incertain embodiments, the light emitter 316 can be configured to emitgreen light. In another example, the light emitter 316 can emit infraredlight. In still further examples, the light emitter 316 can beconfigured to emit light in another frequency band of light.

The light emitter 316 can be disposed adjacent to a cavity 318 thatextends toward the sensor window 314 a. In some embodiments, the cavity318 may have a shorter width than that of the sensor window 314 a,although this configuration is not required. The cavity 318 can besealed with a lens that, in certain embodiments, may be either opticallydiffusive or optically transmissive.

As with the light emitter 316, the light detector 322 can be disposedadjacent to a cavity 324 and below a lens that, in certain embodiments,may be either optically diffusive or optically transmissive.

The depicted embodiment also includes a reflective coating or surface330 (collectively, the “reflective surface”), which, as illustrated, maycontour to the geometry of the sensor windows 314 a, 314 b and thecavities 318, 324. In one embodiment, the bottom surface 312 can take asubstantially flat shape such as shown in FIG. 3B. In other embodiments,the bottom surface 312 can take a substantially convex shape such asshown in FIG. 3C.

Independent of shape, the reflector 330 can serve the dual purpose ofproviding a reflector for both the light emitter 316 and the lightdetector 322 while also providing a reflective surface to redirect lightexiting a measurement site. For example, FIG. 3D depicts the simplifiedcross-section of FIG. 3B, showing a set of example light paths from alight emitter through a measurement site 310 of a subject to a lightdetector of the optical sensing system. As illustrated, light emittedfrom the light emitter 316 passes into an illumination area 336 of themeasurement site 310, through an intermediate volume 328 of themeasurement site 310, to a collection area 338 of the measurement site310, and, thereafter, exits the collection area 338 where it may becollected by the light detector 322 and conveyed to the wearableelectronic device 300. In some embodiments the reflective surface may beshaped to focus reflected light at a particular point or otherwise shapelight exiting or entering the respective cavities.

As noted above, in certain embodiments, the bottom surface 312 can takea substantially flat shape such as shown in FIG. 3D. In otherembodiments, the bottom surface 312 can take a substantially convexshape such as shown in FIG. 3E.

Additionally, as illustrated, the sensor windows 314 a, 314 b can bespatially separated by a particular distance.

As with the embodiment depicted in FIG. 2B, a portion of the lightemitted from the light emitter 316 may not exit the intermediate volume328 through the collection area 338. Correspondingly, a greater portionof the light emitted from the light emitter 316 can be reflected by thereflector 330 back into the intermediate volume 328. The recovered lightcan thereafter be reflected, diffused, or absorbed by the tissue of theintermediate volume 328. In the case that the recovered light is eitherreflected or diffused by the tissue of the intermediate volume 328, therecovered light may have another opportunity to exit through thecollection area 338. In these embodiments, the quantity of lightcollected by the light detector 322 may be greater than the quantity oflight received by the light detector 122 of FIG. 2B.

Similarly, the extended portion 332 of the reflector 330 can reflectlight recovered light back into the intermediate volume 328 across thearea extending between the sensor windows 314 a, 314 b. Moreparticularly, the extended portion 332 can guide light exiting theintermediate volume 328 toward the collection area 338 by repeatedlyreflecting the light back into the intermediate volume 328.

Other wearable electronic devices may include a reflective surfacehaving different geometry than that shown in FIGS. 3A-3E. For example,FIG. 4A depicts a bottom surface of a wearable electronic device 400having two separated reflective surfaces 402. In such an example, thereflective surfaces can be formed as rings of reflective materialsurrounding one or more apertures associated with a light emitter and/ora light detector. In other embodiments, an optical sensing system caninclude more than one pair of sensor windows associated with more thanone light emitter and more than one light detector, such as shown inFIG. 4B. In such an embodiment, a single optical sensing system caninclude more than one light emitter and more than one light detector.Alternatively, a first optical sensing system can be associated with afirst pair of sensor windows and a second optical sensing system can beassociated with a second pair of sensor windows.

In one embodiment, a first light emitter can be disposed symmetricallyopposite a first light detector (e.g., top and bottom sensor windows asillustrated in FIG. 4B) and a second light emitter can be disposedsymmetrically opposite a second light detector (e.g., left and rightsensor windows as illustrated in FIG. 4B). In such an embodiment, thefirst light emitter can be configured to emit light in a first frequencyband of light and the second light emitter can be configured to emitlight in a second frequency band of light.

For one non-limiting example, the first light can be configured to emitgreen light whereas the second light emitter can be configured to emitinfrared light. Correspondingly, the first and second light detectorscan be configured to receive green and infrared light, respectively. Inthese embodiments, the light emitted from the first light emitter can bemodulated differently from the light emitted by the second lightemitter. In this manner, the first and second light emitters can operateat substantially the same time without mutually interfering. In otherembodiments, the first and second light emitters can be configured tooperate in a sequence (e.g., first light emitter active, second lightemitter active, first light emitter active, second light emitter active,and so on). In other embodiments, an arbitrary pattern can be used.

In still further embodiments, a single sensor window can be positionedabove both a light emitter and a light detector, each associated with adifferent optical sensing system. For example, the top sensor window asillustrated in FIG. 4B can be positioned above a light emitter that isassociated with a light detector positioned below the bottom sensorwindow of the same figure. In addition, the top sensor window asillustrated in FIG. 4B can also be positioned above a light detectorthat is associated with a light emitter positioned below the bottomsensor window of the same figure. In this manner, more than one opticalsensing system and/or light emitter and detector pair can be disposedbelow a single sensor window.

In still further embodiments, the first light emitter can be associatedwith a light detector that is disposed to be axially symmetric thereto.For example, a first light emitter can be configured to operate with afirst light detector positioned adjacent to the first light emitter(e.g., top and left sensor windows as illustrated in FIG. 4B). In thismanner, multiple measurement sites can be measured with a single opticalsensing system. For example, in an embodiment in which each sensorwindow of FIG. 4B is positioned above both a light emitter and a lightdetector, twelve possible combinations of light emitter and lightdetector may be possible (e.g., top emitter with right detector, topemitter with bottom detector, and so on). In still further embodiments,a light emitter can be configured to operate with a light detectordisposed below the same sensor window. In these embodiments, fouradditional measurement areas can be measured in order to obtainadditional information about the characteristics of the measurementsite.

In other embodiments, reflective surfaces can have different reflectiveproperties. For example, as shown in FIG. 5, a wearable electronicdevice 505 can include a first reflective surface 502 having a firstreflectivity characteristic (e.g., reflecting a certain frequency band,absorbs a certain frequency band, etc.), and a second reflective surface504 that has a second reflectivity characteristic. In still furtherembodiments, the entire bottom surface of a fitness or health trackingsystem may form a reflective surface, such as depicted in FIGS. 6A-6B.

In some embodiments, the bottom surface of the fitness or healthtracking system that surrounds apertures provided for sensors within thefitness or health tracking system (e.g., optical sensing systems) can bemade from an optically reflective material so as to form a reflectivesurface, such as depicted in FIG. 6A. In other embodiments, the bottomsurface 600 of a wearable electronic device can include a firstreflective surface 602 having a first reflectivity characteristic (e.g.,reflecting a certain frequency band, absorbs a certain frequency band,etc.), and a second reflective surface 604 that has a secondreflectivity characteristic, such as depicted in FIG. 6B. In theseembodiments, the first reflective surface 602 can be configured toreflect light within a first frequency band of light and the secondreflective surface 604 can be configured to reflect light within asecond frequency band of light. In some examples, the first and secondreflective surface 602, 604 can be configured to reflect light withinoverlapping frequency bands of light. For one non-limiting example, bothreflective surfaces can be reflective to light within the visiblespectrum, while the second reflective surface 604 is transparent tolight within the infrared spectrum. In this manner, the bottom surface600 of the wearable electronic device can appear to a user to form asubstantially continuous mirrored surface.

Although many embodiments described herein refer to an optical sensingsystem having a reflective surface, such a configuration is notrequired. For example, in certain embodiments, an existing surface ofthe housing of a wearable electronic device can be coated with a mirrorlike coating. For example, a polished metal coating may be appliedaround or between the one or more apertures associated with the opticalsensing system. In other examples, a thin metallic layer can bedeposited via vapor deposition or another suitable process. Morespecifically, aluminum or chromium may be deposited via vapor depositionto create a highly reflective surface proximate to or between the one ormore apertures associated with the optical system.

In these embodiments, the coating can be applied to the housing of thewearable electronic device or, in the alternative, can be applied in alayered fashion beneath another optically clear layer. Moreparticularly, a coating can be applied to an inside surface of atransparent material (e.g., glass, sapphire, zirconia, etc.).Thereafter, in some embodiments, a subsequent layer may be applied overthe coating. In this manner, the coating may be sealed from environmentsto which the wearable electronic device may be exposed.

In other examples, the reflective surface may be formed from a materialthat is reflective to infrared light but absorbs visible wavelengths. Inthese examples, a reflective coating may appear as a darkened orotherwise opaque area that may be cosmetically indistinguishable fromother portions of the housing of the wearable electronic device.

In still further examples, the reflective surface may utilize or exploitdiffuse reflectivity. More particularly, the reflective surface may beformed from a material that diffuses light. In one example, an opticallywhite ink layer can be applied proximate to or between the one or moreapertures associated with the optical sensing system. In theseembodiments, the lenses associated with the light detector and/or lightemitter may be similarly formed from a diffuse material.

In still further embodiments, the reflective coating may be configuredto be reflective to a particular frequency band of light. In oneexample, a reflective coating may be reflective to green light only. Insuch an example, the light emitter may be configured to emit green lightand the light detector may be configured to collect green light. Inother examples, different frequency bands may be used. In still furtherexamples, more than one frequency may be used. More particularly, thereflective coating can be reflective to one or more bands of light, andcan absorb all or substantially all other bands. In these examples, thefrequency band of lights that the reflective coating reflects can be theband of light that the light emitter is configured to emit and that thelight detector is configured to collect.

In still further embodiments, an additional coating may not necessarilybe required. For example, one or more areas of an aluminum housing of awearable electronic device can be polished to a mirror finish. In theseexamples, either the entire housing of the wearable electronic devicecan be polished to a mirror finish (or, alternative to a mirror finish,polished to a high degree to increase optical reflectivity), or distinctportions of the housing may be polished to increase opticalreflectivity.

In still further embodiments, one or more of the reflective coatingsand/or reflective coating and/or reflective surface finishes may be usedin conjunction to increase the quantity of light received by the lightdetector of an optical sensing system.

Although many embodiments described herein refer to an optical sensingsystem with a single light emitter and a single light detector, such aconfiguration is not required. For example, in certain embodiments morethan one light detector can be configured to collect light initiallyemitted from a single light emitter. In addition, more than one lightemitter may be configured to emit light to be collected by a singlelight detector. In certain embodiments light emitters and lightdetectors can be included in pairs that are configured to emit andcollect light at different frequencies. For example, a first lightemitter and light detector pair may be configured to emit and collectlight in a first frequency band and a second light emitter and lightdetector pair can be configured to emit and collect light in a secondfrequency band. In such embodiments, the first light emitter can bedisposed adjacent to the same aperture as the second light emitter and,correspondingly, the first light detector can be disposed adjacent tothe same aperture as the second light detector. In alternativeembodiments, the first light emitter can be positioned in the sameaperture as the second light detector, and the second light emitter canbe positioned in the same aperture as the first light detector.

Further, although many embodiments described herein refer to an opticalsensing system with a dedicated light emitter and a light detector, sucha configuration is not required. For example, in some embodiments, thelight emitter and/or light detector may also be associated with otherfeatures, functions, or operations of a wearable electronic device oroptical sensing system. For example, a fitness or health tracking systemcan include a status-indicating light emitting diode to convey to a useran operational state of the fitness or health tracking system. In suchan embodiment, the status-indicating light can be used as the lightemitter of an optical sensing system. In this manner, both the lightemitter and the light detector of an optical sensing system can beoperated in one or more modes. For example, in one case, a lightdetector can be operated as a light emitter (e.g., light emitting diodeand phototransistor). Similarly, a light emitter or light emitter can beoperated as a light detector (e.g., phototransistor and light emittingdiode).

FIG. 7 depicts example steps of a method of operating an optical sensingsystem. The method can begin at operation 700 in which light can beemitted toward a measurement area. At 702, light exiting the measurementarea from a first sub-area of the measurement area can be reflected backinto the measurement area. At 704, light exiting the measurement areafrom a second sub-area of the measurement area can be received.

Many embodiments of the foregoing disclosure may include or may bedescribed in relation to various methods of operation, use, manufacture,and so on. Notably, the operations of methods presented herein are meantonly to be exemplary and, accordingly, are not necessarily exhaustive.For example, an alternate operation order, or fewer or additional steps,may be required or desired for particular embodiments.

The foregoing description, for purposes of explanation, used specificnomenclature to provide a thorough understanding of the describedembodiments. However, it will be apparent to one skilled in the art thatthe specific details are not required in order to practice the describedembodiments. Thus, the foregoing descriptions of the specificembodiments described herein are presented for purposes of illustrationand description. They are not meant to be exhaustive or to limit theembodiments to the precise forms disclosed. It will be apparent to oneof ordinary skill in the art that many modifications and variations arepossible in view of the above teachings. In particular, any featuresdescribed with respect to one embodiment may also be used in otherembodiments, where compatible. Likewise, the features of the differentembodiments may be exchanged, substituted, or omitted where compatibleand appropriate.

The present disclosure recognizes that personal information data,including biometric and/or physiological data, in the presenttechnology, can be of benefit to users. For example, the use ofphysiological or medical data can inform a user of the user's generalhealth. In other examples, user medical data can be anonymouslycollected for providing to authorized medical professionals informationabout the health or fitness levels of a geographic or demographic groupof patients. Further, other uses for personal medical or healthinformation data that benefit the user, including biometricauthentication data, are also contemplated by the present disclosure.

In addition, the present disclosure contemplates that the entitiesresponsible for the collection, analysis, disclosure, transfer, storage,or other use of such personal information or data will comply withwell-established privacy policies, privacy practices, and/or individualprivacy preferences of particular users or authorized third parties. Inparticular, such entities should implement and consistently use privacypolicies and practices that are generally recognized as meeting orexceeding industry or governmental requirements for maintaining personalinformation data private and secure, including the use of dataencryption and security methods that meets or exceeds industry orgovernment standards. For example, personal information from usersshould be collected for legitimate and reasonable uses of the entity andnot shared or sold outside of those legitimate uses. Further, suchcollection should occur only after receiving the explicit and informedconsent of the users or a user's legal guardian or representative.Additionally, such entities would take any needed steps for safeguardingand securing access to such personal information or data and ensuringthat others with access to the personal information or data adhere totheir privacy policies and procedures. Further, such entities cansubject themselves to evaluation by third parties to certify theiradherence to widely accepted privacy policies and practices.

Despite the foregoing, the present disclosure also contemplatesembodiments in which users selectively block the use of, or access to,personal information data, including biometric and medical data. Thatis, the present disclosure contemplates that hardware and/or softwareelements can be provided to prevent or block access to such personalinformation data. For example, users can select to remove, disable, orrestrict access to certain health-related applications collecting users'personal health or fitness data.

What is claimed is:
 1. An electronic device comprising: a housingdefining an aperture; an optical sensing system comprising: a lightemitter for emitting light through the aperture, the light emitterpositioned adjacent the aperture; and a light detector for obtaining afirst portion of the light after the first portion of the light reflectsfrom an object; and a reflector disposed about the aperture and adaptedto reflect a second portion of the light back into the object after thesecond portion of the light reflects from the object.
 2. The electronicdevice of claim 1, wherein the reflector comprises an opticallyreflective material disposed around a perimeter of the first aperture.3. The electronic device of claim 1, wherein: the aperture is a firstaperture; and the housing defines a second aperture, wherein the lightdetector is positioned adjacent the second aperture.
 4. The electronicdevice of claim 3, wherein: the reflector is a first reflector; and theelectronic devices further comprises a second reflector disposed aboutthe second aperture and adapted to reflect light exiting from orreflecting off the object back into the object.
 5. The electronic deviceof claim 4, wherein the second reflector comprises an opticallyreflective material disposed around a perimeter of the second aperture.6. The electronic device of claim 3, further comprising: a first sensorwindow positioned over the light detector and disposed within the firstaperture; and a second sensor window positioned over the light emitterand disposed within the second aperture.
 7. The electronic device ofclaim 6, wherein the first sensor window is adapted to focus light ontothe light detector.
 8. The electronic device of claim 6, wherein thefirst and second sensor windows are configured to diffuse light passingtherethrough.
 9. The electronic device of claim 6, wherein the firstsensor window transmits a first frequency band of light and reflects asecond frequency band of light.
 10. The electronic device of claim 9,wherein the first frequency band of light comprises infrared light andthe second frequency band of light comprises visible light.
 11. Theelectronic device of claim 6, wherein the second sensor window transmitsa first frequency band of light and reflects a second frequency band oflight.
 12. The electronic device of claim 11, wherein the firstfrequency band of light comprises infrared light and the secondfrequency band of light comprises visible light.
 13. The electronicdevice of claim 1, wherein: the light emitter comprises a light emittingdiode; and the light detector comprises one of the group consisting of aphotodiode, a phototransistor, or an optical image sensor.
 14. Theelectronic device of claim 1, wherein the electronic device isconfigured to be worn on a wrist of a user, and wherein the electronicdevice further comprises: a processor disposed within the housing andcoupled to the optical sensing system; a display in communication withthe processor; a button in communication with the processor; a rotaryinput device in communication with the processor; and a battery disposedwithin the housing and coupled to the processor.
 15. An optical sensingsystem comprising: a light emitter for emitting light toward ameasurement site of an object; a light detector for receiving lightexiting a first sub-area of the measurement site; and a reflectorproximate the light emitter and adapted to reflect light exiting asecond sub-area of the measurement site back toward the measurementsite.
 16. The optical sensing system of claim 15, wherein: the reflectoris a first reflector; and the optical sensing system further comprises asecond reflector proximate the light detector and adapted to reflectlight exiting the first sub-area of the measurement site back toward themeasurement site.
 17. The optical sensing system of claim 15, wherein:the light emitter is configured to emit light in a frequency band oflight within a visible spectrum of light; and the light detector isconfigured to receive light at least within the frequency band of lightemitted by the light emitter.
 18. The optical sensing system of claim17, wherein the light emitter is configured to emit light in a greenspectrum.
 19. The optical sensing system of claim 15, wherein: the lightemitter is a first light emitter; the light detector is a first lightdetector; and the optical sensing system further comprises: a secondlight emitter for emitting light in an infrared light spectrum towardthe measurement site; and a second light detector for obtaining infraredlight exiting the measurement site.
 20. The optical sensing system ofclaim 19, wherein the second light emitter is positioned proximate thefirst light detector and the second light detector is positionedproximate the first light emitter.
 21. The optical sensing system ofclaim 15, wherein the light emitter is configured to be operated in alight emitting mode and a light receiving mode; and the light detectoris configured to be operated in a light emitting mode when the lightemitter is operating in the light receiving mode and in a lightreceiving mode when the light emitter is operating in the light emittingmode.
 22. A method of optical sensing, comprising: emitting light towarda measurement site of an object; receiving light exiting a firstsub-area of the measurement site; and reflecting light exiting a secondsub-area of the measurement site back toward the measurement site. 23.The method of claim 22, wherein the operation of emitting lightcomprises emitting light in a frequency band of light within a visiblespectrum.
 24. The method of claim 22, wherein the operation of emittinglight comprises emitting light in a frequency band of light within aninfrared spectrum.
 25. The method of claim 22, wherein the operation ofreflecting light exiting the second sub-area of the measurement siteback toward the measurement site comprises reflecting light in afrequency band of light within a visible spectrum.
 26. The method ofclaim 22, wherein the operation of receiving light exiting the firstsub-area of the measurement site comprises receiving light in afrequency band of light including a visible spectrum and an infraredspectrum.